Stmicroelectronics S.r.l.

Maria Luisa Polignano

Francesco Cazzaniga

Anna Paola Caricato

Federica Zanderigo

Giuseppe Pavia

Daniele Caputo

Marzio Brambilla

An interface between a semiconductor substrate/dielectric layer is characterized through measurements of a photocurrent. The photocurrent is induced in the semiconductor substrate by scanning a certain area of the interface with a laser beam and which is collected via a Schottky contact. The Schottky contact is established by inversely biasing a first electrolyte with respect to a potential of the bulk of the semiconductor substrate. The first electrolyte is capable of etching any native or thermal oxide that may exist on the contact area with the semiconductor substrate. The surface potential of the semiconductor substrate/dielectric interface is controlled by a gate electrode established on the dielectric layer by way of a second electrolyte. The second electrolyte is not aggressive to the dielectric material and is biased by an electrode immersed therein with respect to the potential of the bulk of the semiconductor substrate.

Characterization of a semiconductor/dielectric interface by photocurrent measurements

The depth of a denuded layer with respect to a relatively defective bulk region of a monocrystalline semiconductor wafer is estimated in a nondestructive way. The depth is determined by measuring the lifetime or diffusion length of injected excess minority charge carriers on a surface of the wafer having such a denuded layer and on a different portion of the surface of the wafer from where the denuded layer has been previously stripped-off by lapping and/or etching. The depth is calculated through a best-fit procedure or through numerical processing of the measurement results on the basis of the diffusion equations of excess minority carriers.

Determination of the thickness of a denuded zone in a silicon wafer

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Cambiago, Italy

Maria Luisa Polignano